Code stack



Jan. A12, 1965 A. BROTHMAN ETAL CODE STACK Filed July 19. 1961 8 Sheets-Sheet l Jan. 12, 1965 Filed July 19. 1961 ITT-Enga.-

BROTHMAN ETAL CODE STACK 8 Sheets-Sheet 2 Jan. 12, 1965 A. BRoTHMAN ETAL 3,155,733

com: smcx Filed July 19. 1961 8 Sheets-Sheet 4 Jan. 12, 1965 A. BROTHMAN ETAL 3,165,733

CODE STACK 8 Sheets-Sheet 5 Filed July 19, 1961 BNN.

el wml www Jan- 12, 1.965 A. BROTHMAN ETAL 3,165,733

` CODE STACK Filed July 19. 1961 8 Sheets-Sheet 6 F1- Em .25.

Jan. 12, 1965 CODE STACK 8 Sheets-Sheet 7 Filed July 19. 1961 Jan. l2, 1965 lA. BRoTHMAN ETAL 3,165,733

CODE STACK 8 Sheets-Sheet 8 Filed July 19. 1961 mmlmhurl United States Patent() 3,165,733 CODE STACK Abraham Brothman, Dumont, and Richard D. Reiser, Newark, NJ., Stephen J. Halpern, Forest Hills," N DY., and Edward W. Lewison, Englewood Clitfs, and Paul vbewison and Alfred Lewison, Deal, NJ., assignors, by mesne assignments, to Transitel international Corp., Paramus, NJ., a corporation of New Jersey L Filed .lul-y 19, 1961, Ser. No. 125,247 13 Claims. (Cl. S40- 347) This invention relates to code stacks and more particularly to code stacks for rotatable shaft output devices wherein shaft angle positions are translated into a binary code.

Shaft angle encoders presently in use are usually of the disc or cylinder type wherein the former has its encoding pattern on the ilat surface while the latter has its encoding pattern on its curved; surface. The shaft encoders are used to give a binary coded representation for each shaft angle position. The shaft encoder is able to provide a high degree of accuracy of conversion from shaft rotation to binary digital code without going through intermediate electronic analog operations. The accuracy of the shaft position encoderis built into the encoder by mechanical means and-therefore isnot subject to drift or the need for adjustments. e l Y The disc type of shaft angle encoder normally consists of a plurality of circulartracks, one for each binary digit of the digital representation, wherein each track contains a plurality of arcuate segments. The varcuate segments are normally made conductive whereas ythe area between segments is non-conductive. The brushes 'used to sense the conducting segments are mounted on a lsingle radial line. The electric circuit through the arcuate segments and the sensing brushes is completed through `a common brush and a continuous segment-or 'a ring which iselectrically connected to all segments. The dimension of each conductive segment is chosen to correspond to the changes in binary digits in the binary coded representation of eachv Y* position. n

The angular positions whicha shaft may assume are iniinite in number. This being true there exists the pssibility 'that one of the positions which the shaft may assume is a position at the intersection of two distinctdecimal numbers. For example, in a meter designed toxread in the; decimal system, the dial pointer may assume any angular position on the hairline between theposition number land the position number 2. The binary representation of .the decimal digit on the code wheel'is such that ambiguity` arises at the `exact position at lwhich the dial indicator is moving Vfrom the decimal number' 1 to the decimalnumber 2. That is, .at this point, atleast one of thesensin'g lbrushes is makingthe transition" from van y insulated portion of the code wheel to a. conductive-seg ment. Unless the dimensional tolerances on the segments.

and brushes are-.reduced toabsolutezero, the transition from conductive segment to insulated portion on the disc vwill not be sharp. .Although this occurrence is not'se'rious with regard to thetrack on the disc which represents the least significant binary digit, the prohlemdoes become a serious one when the two outputs' are notimrnediately adjacent one another with regard to their chronological order. For example, in a case where the shaft encoder has-.four tracks eachirepresentmg a` binary digit and the discv is rotated fromthe'position lwhich vrepresents the position which f represents the decimal Y `number 9 to the decimal number. zero. Letting the number. llrepresent l a lbinary one. and. 0represe`nt 'a binary Zero,-thel .binaryr'e'presentation for'the decimal numbergis 100,1 while the binary representation lfor the decimal `number .0- is 0000. It can kbe seen here that the most signifcantand *l 'brushfto make electrical contact with these extraseg the least binary digity positions are changing simultaneously.

lf for example, at the midway point between decimal 9 and decimal 0 with the track which represents the decimal number 8 remains in Contact with its conductive segment for a longer period than does the sensing brush for decimal l position due to the practical limitations of sensingbrush alignment, then the binary representation will be i000 which represents the decimal number 8 which does not represent a position midway between 9 and 0. Thus it can be seen that the ambiguity need not be limited to the least significant digit, but may occurv along any track of the binary representation. y To better illustrate this phenomena, consider for exam# ple, the binary coded decimal with an even parity bit. In this system, the Adecimal numbers 0 through 9 are represented as in Table l, with the parity bit position being in Binary l state in those decimal numbers whose binary representationcontains an odd number of binary l bits.

ln those decimal numbers whose binary representation contains an even number of binary l bits the parity will be in binary 0 state. From Table l we see that the code for decimal number 3 is 00011, while the code for binary 4 isl0100. Due to misalignment of the code stack and/ or the sensing brushes, as the code stack transfers from decimal position 3 to decimal 4, for example, the sensing brush of the binary l'bit position and. that of the.4 bit position may lead the other sensing brushes; theymay, therefore, arrive at the arcuate portion of the code stack which represents decimal/4 while the other three brushes remain on that portion of the code stack which represents decimal 3. The resulting code will be 00110L which is a correct code for the decimal 6` and will pass all parity checks. Thus it can be seen that the ambiguity problem must be solved in encoding devices of the above-mentioned type before any degree of accuracy can be obtained.l

T abile 1 Parity `Decimal value Onernetho'diof avoiding such an ambiguity Vis to design wherein good electrical Contact occurs only at the central region of theconductive segments. Failure ofthe extra `ments completelyA inhibits the reading. This method has the disadvantage of'failing to produce coded representaf tion of all halfway preventing the encoders use inwmany applications. Another. solution is the providing' ofaa mechanical scheme 'for the shifting of segments in one Q'direotion or the 'other 'when ythe brush arm is located at the boundary i between aconductor' and aninsulating portion .on` the disc. This 'arrangement which requires a large number 4of moving parts,l imposes fspeed limitations upon the encoder .v thereby. severelyelimiting its .widespreadapplication.V Another g method" `of avoiding \.alnliguities at, sectorl boundaries whichis widely in use is 4the double brush method. `In this method, two sets of brushes are required when positions of they brush arm thereby j Vity zones.

the method is used with commutative segment-s in the normal ffashion. The least significant digit of the tota-l binary representation has 4but one sensing brush while every other track has two sensing brushes. One sensing 4brush in each two brush track is positioned ahead of the position being encoded while the remaining brushes in leach two brush track is positioned behind each position being encoded. The separation between the two brushes of each track is equal to the width (or angle in the case of the disc encoder) of the conductive segment on the track representing the least significant binary digit. The double brush method is set forth in greater detail'in the text by R. K. Richards entitled Digital `Computer Components and Circuits, copyright `1957 by Van Nostrand, on pages 471- 477. IBasically, the double brush method consists of an examination vof the preceding brush position to ascertain the reading of the preceding sensing brush. Once the reading of the preceding brush y(that is the brush which senses the next least significant binary bit of the binary representation) is ascertained, its binary value determines which `one of the two brushes reading the next binary bit is to be chosen for this particular reading. This decision is performed by logical switching circuits. This method of encoding in orde-r to avoid the ambiguity therefore requires substantially twice the number of sensing brushesV in its construction and also requires logical switching circuitry between each binary position thus greatly increasing the complexity of the shaft encoder.

The V-scan method of avoiding ambiguities which is also set forth inthe text by R. K. Richards set -forth above on pages 473-477 is quite similar to the double brush method but .one major distinction lies in the fact tha-t a logicaldecision of the nature of that made in the double method is required to be made after the sensing of each binary digit, whereas in the double brush method the decision is made only once upon the sensing of the least significant binary digi-t. The V-'brush method there-fore requiresa larger number of decision making circuits thereby increasing the number of components `and the complexity of the encoder.

` The device of our invention overcomes the ambiguities v of the types discussed above while at the same time avoiding theneed yfor any logical decision making circuits associated with` the encoder orl the transmitting means thereof. Our invention consists of a code stack which is comprised of a-plurality of conductive discs which are alternately disposed Ybetween insulating discs. The insulating discs :are arranged to form channels between adjacent insulating discs the walls of which guide the sensing :brush and maintain it in proper alignment at all times. The stack of discs is positioned upon a rotable shaft which is reading which reading can be recognized as a valid reading when accompanied Iwith a binary one in the ambiguity bit position. n

One practical applica-tion of our novel encoder lies in the utility meter area wherein meters ysuch as water, gas or electric meters having a plurality of visually readable dials are designed to have their dial readings encoded for automatic reading thereof. An automatic meter reading system tof this ltype is set forth in U.S application Serial lNumber 71,093, now Patent No. 3,096,932, entitled Automated Meter Reading System, by A. Brothrnan et al., filed February 23, 1961, and assigned to the assignee `of the instant invention. usually arranged with a set of dials in which the rotatable shafts for each dial are appropriately vgeared down by an intricate gearing system. During rotation of the gearing system engaging gears experience both radial and tangential iforces originating from the gears with which they are meshed. `in gas and Water meters, the power available to drive the indicating register is sufficiently large so that a small amount `of added tangential drag will not effect the accuracy of the device a noticable amount. However, watt-hour metersare driven by an eddy current motor whose power output is relatively small and, in addition, there are no formal bearings in the meter register. For these reasons, the permissible drag torque applied to the shaft of a watthour meter lby the Isensing brushes of an encoder, must be kept to a minimum. Since lit is impossible to mechanically sense the surface of an encoder without applying some force, we used the novel idea of making the applied force directly oppose the normal separating forces of the gear train. In any set of spur gears, the force applied by the driving tooth to the driven tooth is a force composed of a tangential or dri-ving component, and a radial component commonly called the separating force. Thus, our encoder in yfact, acts as an additional bearing means and, therefore, applies no measurable amount of drag to this sensitive instrument.

The coding of the code stack is arranged so thatthe binary representation for each decimal number is unique from they binary representation for any other decimal number. In addition, ambiguity readings are easily dist cernible from non-ambiguity readingsdue-to the presence inserted through the axis .of the code stack and is iixedly secured thereto. One end of the rotatable Yshaft is operatively connected .to a prime mover while the opposite end has a'dial indicator rixedly secured thereto .which cooperates with a diall to produce a visual reading `of the angular position of the shaft.V

v.The conductive discs have irregularly or cam-shaped perimeters which are formed in accordance Withthe unique code of our invention. lThe cut away or notched portions `of the conductive discs cooperate with fthe raised portions of the adjacent insulating discs to forma continuous cirf' cular perimeter. p

A sensing brush bears upon an associated conductive disc and acts to complete the electrical contact between the codestack and the'input to the device utilizing the coded representations of the position of the rotatableshaft.

f The unique code arrangement .of the code stack contains adisc havingbinary l positions which indicate ambigu- This conductive disc is so `arranged that it' lemits a binaryv one -for angular shaft positions vwhichi lie between shaft positions `representing the. intersections ,be-

tween adjacent decimal integers O through 9.l Thus, in-

stead of trying to avoid the possibility of arr-'ambiguous reading, the code is arranged to recognize an ambiguous" of .a binary one in the ambiguity` binary bit position. Each ambiguity reading is likewise easily discernible from another ambiguity rreading' lthus preventing the possibilityV of any false identiiication of any given reading. The binary code selected is of the self-checking type with sutiicient redundancy information to drastically reduce the probability of injecting error-'ed information into thefcommunication link. Furthermore, any alteration .of the coded information due to the properties of the link itself can be detectedat the receiving end. Thus a high degree of accuracy is attainable without the need for error checking circuits at the transmission endof the system.

The individualcomponents of the code-'stack assembly may be produced by regular stamping means. The components are assembled simply by placing each disc of the assemblage upon a shaft and yfastening both ends of the stack.` The code stack assemblage affords greater accuracy than prior art devices without the introduction of additional complexity, expense and fabrication time.

Another preferred embodiment ofthe invention em-,

ploys a coding arrangement which represents each clear,

unambiguous decimal digit in a first binary code and` which represents the region immediately surrounding the intersect-ionbetween two decimal digits,(i.e., the transition yfrom one decimaldigi-t to` the next highestl decimal digit) in a second,binarylcodgand further which repre sents the ajgnaroach of the second vcode by a third oranticipatory code. Y v" 'l I Y Thefiirst `code is an arbitrary or Meters o-f the utility type areV p gray1 code Whose digit positions'have no binary weight. The binary representationnfor Aeach'decimal 'digitdiffcrs from allV otherff binary` codedA 4decimal representations. Each representaan inherent self-checking feature.

The second code differs from the iirst code in that it has a fixed number of binary ones in each decimal representation which are greater in number than the number of binary ones in the decimal representation of the first code.

v The code stack assembly is so `arranged as to intersperse the first and second codes so that they alternate in appearance as the decimai digits advance from 0 through 9.

In order for the output utilization means,` which may be a remote receiver-computer combination, to distinguish betwen the presence of either the rst, second or third code, an ambiguity bit is provided wherein the presence of the ambiguity bit (i.e., a binary one) denotes the presencel of either the second code or the third code and the absence ot the ambiguity bit (binary zero) denotes the presence of the rst code.

The arrangement of the binary ones in the rst code is such that the binary one ypositions in the binary representations for each decimal digit differs from the binary representations on either side by the shift .in position of one binary one, Likewise the binary representations of the second code diter from the representations on either side by the shift in position one by one binary one. In addition to this, each binary representation of the second code contains a binary one in each of the same digit positions in which the first code binary representations on opposite sides of the second code representation contains a binary one. Thus, in making the transition from a binary representation of the first code to a binary representation of the lsecond code and then to the binary representation oi the next succeeding iirst code, the second code representation adds a binary one to the preceding first code representation and then loses a binary one to form the following rst code representation; i

This arrangement insures the fact that only one binary bit positionv makes a transition from one binary state to the opposite binary state in moving rrom one code representation to the 'other throughout the rotation of the code stack. This design eliminates the occurrence of an erroneous reading at a transition position due to a misalignment olf the code stack sensing brushes since the possibil-v ity of obtaining an erroneous indication of a-remote sector of the code stack has been eliminated. v.

The encoding segments of the code stacirare further arranged to permit a large toierance of sensing brush misaiignment by staggering the segments which undergo a transition of binary states. thus eliminating the possibility of deriving an erroneous-reading.

In many-installations the number of shafts whose angular positions are tobe encoded are greater than one. For exanipie, in gas` and electric meters four shafts are `ernployed to control the indicator hands of the four dials which are employed to represent any decimal number from 0000 to 9999.

- Since each rotatable shaft ofthe utility meter requiresy y a code stack, the number torfleads required between the-out puts of the code'staclis and vthe input-ofthe utilizationdef' T vice which receivesthe `encoded data is four times the l number of output` leads ofanyone code stack. The ref' quirenient of a llarge numbery of leads `makes such anzen,

coding yinstallation costly due to the excessnumber of wires needed-and the compieiiity of wiring 'the appropriate Y connections." Y 'y ,V

To overcome this problem, we havef providedy a logical OR circuit arrangement which requires a total number of'leads which'is substantially less than the. numbernof leadsused in prior art encodingdevices. The output leads of the same binary bit position are connected'fto acom-k mon point through equal resistances. The common leads l ,which supply the input voltage-Vlevelv for the decimal Achar-"" `acterfb'eing encoded -arte/Teachbrought out separately so' that they maybe selectively energized to provide va posi- Y tive voltage levelr for V the code stack .of the character being encoded while all other common 'leads are maintained near ground potential.

Since only one decimal character is encoded at a time, only one set of output leads is required. The resistors provide a voltage divider network which assures the tact that:

Where rlfhus the binary representations are easily distinguishable from one another even in the worst possible case where all encoders are in thebinary "1 position ON any particular bit. Binary "0 must always be smaller than whereas binaryl l must always be equal to or greater than NB+ It is, therefore, one object of our invention to provide a shaft angle vencoder having a novel arrangement for recognizing ambiguity readings.l

Another object of our invention is to provide a novel shaft angle encoder which is so arranged as to produce a self-checking feature. Y

Still another of our invention is to provide a shaft angle encoder having a rst code read out for a non? ambiguous reading and a second code readout for ambiguous readings.

Still another object of our invention is to provide ak novel shaft angle encoder for any analog type rotatable shaft meter having at least one dial indicator' wherein the code stack arrangements do not measurably` increase the drag ratiok in meters, so as not to decrease the accuracy of the meter. k

Another'object of our invention is to provide `a novel vmeter comprising Lmeans for encoding the'meter decimal digit reading wherein the encoding arrangement generates a unique code hav-ing a plurality of checking features.

Still another object of our invention is -to providefan encoder for` generating a novel code wherein the periphery of each code discl is congruent to the periphery ot every other code disc of the encoder.

f Another object of ourinvention isto provide ashaft encoder having a pluralityv of conductive andinsulating" `discs whichvvare alternately arrangedsoas to provide elecvn trical insulation, proper alignmentandv continuousguidf ance for the code stack sensing brushes.

VAnother object of our inventionis toprovide a shaft angle encoderv having first and secondalternately :dis-,f persed codes wherein the `representations -of eachiirst code differ from the representations of adjacent iirst code representations by only one digit position.

l Another objectv of our invention is toprovide a "shaith` angie. encoder having first and second alternately Vdis-- persed Lcodes wherein the representations of each second codediierl from the representations of: adjacent second code representations by only one digit position. 1 Y Another object ot. our invention i's to provide a shaft fanglefencoder having tirst and second alternately dis- `,persed codes wherein the representations of each second I Vcode contains a binary one in every digit .position which the neighboring first code representations contain a binary one.

Another object of our invention is to provide a shaft angle encoder having first and second alternately dispersed codes wherein the representations of each second code contains a binary one in every digit position which the neighboring-first code representations contain a binary one and where said iirst and second codes are further distinguished by the selective presence and absence respectively of an ambiguity bit.

These and other objects of the invention will become apparent when reading the following description in connection with the drawings, in which:

FIGURE l is a top view of the code stack assembly.

FIGURE 2 is a perspective view of one conductive disc employed in the code stack assembly of FIGURE 1.

FIGURE 3 is a perspective View of the insulating disc associated with the conductor disc shown in FIGURE 2.

FIGURES 4 through l0 are top plan views of the metallic or conductive discs together with their associated insulating discs, which are employed in the code stack assemblage of FIGURE 1.

FIGURE 11 is a top plan view and force diagram of a pair of meshed gears set forth for the purpose of showing the forces acting on the gears.

FIGURE 12 is a front view of the code stack assemblage of FIGURE 1.

FIGURE 13 is a schematic view showing the electrical connections between the input and output of the code stack assembly.

FIGURE 14 is a schematic view of a portion of the circuit of FIGURE 13 set forth for the purpose of eX- plaining a particular condition which the code assembly assumes during its operation.

FIGURE 15 is a schematic diagram of the binary code employed in the shaft angle encoder of FIGURE l showing all of the conductive segments in relation to one another.

FIGURE 16 is a schematic diagram of another embodiment of the code stack arrangement for the encoder shown in FIGURE `l.

FIGURES 17 through 22 are top plan views of the con ductive discs together with their associated insulating discs, which are employed in the encoder of FIGURE 1 and which are encoded in the arrangement shown in FIG- URE 16.

FIGURE 23 is a front view of a meter which may be combined with our novel code stack and which alsov serves to illustrate the novelty of our invention.

FIGURE 24 is a modified coding arrangement of the code shown in FIGURE 16. Referring now to the drawings., FIGURE l shows code stack assemblage 2,5 which is comprised of a plurality of insulating discs 11 through 17 and conductive discs 13 through 24 ywherein each conductive disc 1S through 24 is separated from the neighboring conductive discs by insulating discs 11 through 17. Thecode stack 25 which'is comprised .of discs 11 through 24 is mountedrfor-rotation' upon rotatable shaft 26 `which shaft is rotated by gear 27 which is Xedly secured tothe shaft 26. Gear 27 may, for example, b e theoutput gear of an electric'watt-hour meter'whichfdrives'shaft 26 so as to produce a visual reading of the units digit in kilowatt hours. The opposite end 2617 of shaft 26 hasa dial pointer 27a fixedly secured to the shaft. Pointer 27a cooperates with a dial face (not shown) located on faceplate 2S. The. dial face isV ar- 4.ranged in the vusual way wherein the angular position of lshaft 26 is determined by the position of pointer 27a with regard to the vassociated dial faceon face plate 28. The

ein face normally has the decimal numbers orhroughs equally spaced around the dial face. Although only one encoder is described,.it'should be understood that a` greater number of encoders may be employedfeach one ,beingjv associated with a diiferent dial lface. It should further be brushes or members 31 through 37 which cooperate with conductive `discs 1S through 24 respectively. The read out from sensing brushes 31 through 37 is a parallel read out which serves as an input to a utilization device. One such device which may utilize the read out from sensing brushes 31 through 37 is set forth in copending U.S. application Serial Number 126,278, led July 24, 1961, entitled Data Transmitter, By A. Brothman, and assigned to the assignee of the instant invention. The data transmitter Set forth in the aforementioned application accepts the parralled read out from code stack 25; converts the read out to a serial read out; and transmits the read out in serial fashion to a centrally located data gathering point. The aforementioned data transmitter is set forth only as one possible utilization device for the instant invention and therefore plays no part in the novelty of my code stack but is set forth as being merely exemplary.

Sensing brushes 31 through 3'7 are inserted through holes (not shown) in post 38 and are secured in any suitable manner to the post which is in turn fastened to dial face plate 28 by fastening means consisting of a screw 41, lock washer 40 and resilient washer 39. Post 38 is formed of an insulating material in order to prevent any shortcircuiting among the sensing brushes 31 through 37 fastened thereto.

The code employed in code stack 25 is a six bit binary code wherein reading from the least to the most significant bit the tracks represent 0,A l, 2, 3, 6 and Ambtwhich represents ambiguities as will be more fully described). The conductive discs representing each of these positions are 19, 20, 21, 22, 23 and 24 respectively. Conductive disc 1S carries the designation of the Common. wherein the sensing brush 31 associated with the common disc 18 serves to establish electrical continuity with other conducting discs 19 through Z4 by means of fastening bolt 29 which makes electrical contact at all times with each and every conductive disc 19 through'24.

In order to represent in binary code the decimal digits 0 through 9, the Vconductive discs 19 through 24 are arranged so that not all discs 19 through 24 are in electrical lcontact with their associated sensing brushes 32 through 37 during the entire cycle of rotation -of rotatable shaft 26. ThusV it can be seen that discs 19 through 24 are coded in such a fashion as to make electrical contact with i theirvassociated sensing brushes 32 through 37 at certain specified periods throughout their cycle of rotation and to be insulated during the remaining periods. The binary lcoding set forth above is normally known as the 2 out of 5'code. For example, to represent the decimal number 4, sensing brushes 33 and 35 must make electrical contactl with their associated brushes whereas `sensing brushes 32, i

,'1 represents electrical connection). y As'another example, the decimal number 7 requires sensing-'brushesl 33V and 36 to make electrical lContact with their .associated discs Ztl and 23 while sensing brushes 32, 34', 35 and v37 rvmust be electricallyjinsulated from their associated discs,

thus producing the output 010010. The v'preceding examy ples hold true when pointer 27a is either exactly half-way between thei dial face positions of two `adjacent decimal digits or is relatively close thereto. However, when pointf er 27a stands either exactly over `a decimal digit position v or in the regions immediately before and after the decimal digit position on the dial face such as'decimal digit 2 for example, the code stack 25 must provide accurate'recogni-l t -2 tout of v5 binary-cod tion of this angular position so as to avoid the possibilty of an erroneous reading which may occur as set forth in the introductory remarks above. The conductive disc 24 which provides the Ambiguity read out position indi- Cates such an intersection or transition position in a manner to be more fully described.

The discs il through 243 have coniigufations which are clearly set forth in FIGURES 4 through 10. In conformity with the "2 out of 5 code, EEGURES 2 and 3 show clearly the manner in which the sensing brushes 32 through 37 are selectively connected and disconnected from their associated conductive discs'l@ through 2d respectively. The disc i9 of FiGURE 2 is formed of a conductive material such as, for example, brass. Disc 1Q is generally circular in shape but has a pair of elongated slots Si and 52 notched along the perimeter of the disc.

FIGURE 3 is a perspective view of the insulating disc lll shown in FIGURE l which cooperates with conductive disc 19 as will be more fully described. The outer diameter di of insulating disc 1l. is greater than the outer diameter of the conductive disc i9. This relationship holds true with respect to each insulating disc and its associated conductive disc which thereby serves to both restrict and guide the sensing brushes 31 through 37 through the groove formed between adjacent insulating discs such as, for example, the groove Fitl formed between insulating discs 16 and i7 as can best be seen in FIGURE l.

Two raised projections 57 and 53 which are integrally molded with insulating disc ill are strategically positioned upon the surrace of disc il to cooperate withslots 51 and 52 cut in conductive disc 19. The raised projections 57 and 53 not only serve to insulate conductive disc 19 from its associated sensing brush 32 during certain portions of the rotation of disc 19, but also serve to rigidly position and secure disc il@ to insulating disc 1l to avoid any relatively angular movement to take place between discs 11.

and 19. This is also true of all othercC-nductive discv insulating disc combinations.

Disc 19 is provided with an aperture 62 through which rotatable shaft Z5 is inserted. Aperture d3 in insulated 'disc 11 also serves to permit insertion oifrotatableshait Zobut it should be noted that aperture 53 is substantially smaller than aperture 62. The reason `for this is that rotatable shaft 2o being formed of a conductive material would electrically connect all of the conductive shafts to the dial face plate 2h. Since aperture 62 is substantially conductive disc l@ (as the central aperturesof all other conductve discs are) is electrically insulated from the' projections 5S Vandi-'7 of insulating disc lll.

Aperture 53 indisc 19 is 'provided for the insertionl of v greater than the outer dimension of rotatable shaft 26 they the discs 19 through 24 which make contact with the associated sensing brush while the spaces between conductive segments are shown by the blank areas in FIG- URE 15. In this diagrammatic representation, in order to better visualize the operation, sensing brushes 31 through 37 should be considered as remaining stationary while the planar development of the conductive segment moves in the direction shown by arrow 13h. Another way of considering FIGURE 16 as a dynamic picture of the code stack is by positioning a sheet of paper having a narrow slit which is perpendicular to `arrow 13d' and moving the paper in a direction opposite to that of arrow 13th When the planar development moves beneath sensing brushes 3l through 37 to a point beyond the right-hand most portion of FIGURE 15, it should be understood that the segments repeat themselves; that is, that the left-hand most portion of FGURE l5 is connected with the righthand most portion of the figure to form an endless belt having predetermined conductive and nonconductive areas.

When the development of FIGURE l5 moves in the direction shown by arrow 13h so that the brushes 31 through 37 are in direct alignment with the decimal numbers 1 through 0 shown at the top of FIGURE 15, the binary representation of each decimal number l through 0 that will appear at the output of the sensing brushes 31 through 37' is set forth in the table 135. It should be understood that the elongated solid segment 18, which represents the common disc of the code stack 25 of FIG- URE l, supplies the voltage level which selectively appears at the sensing brushes 32. through 37 depending naturally upon the angular position of rotatable shaft 26.

it can be seen from table 135 that the coding for each decimal number 0 through 9 has an even number of binary ones thus producing an inherent self-checking feature. That is, upon the occurrence of an odd number of binary ones, 'in any binary representation, itbecomes immediately obvious that amistake has occurred -in the transmission or" the data. Since the probability of the occurrence of a compensating error is very small, the 2 out of 5 code is a very desirable coding'arrangement. it should be understood,V however, that other and diiierent coding arrangements may be used. t l. Since the rotatable shaft'Zd is capable of assuming an infinite number of langular positions throughout its rotation, shaft 2o is not limited to assuming positions in the region between the decimal digit positions of the decimal numbers l through 0' (on the dial face) as shown at the top of FGURE 16 but shaft 2d may occupy positions during its rotataion such that upon'a read out request, sensing brushes 32 through 37 occupy a position either` exactly over or immediately near a decimal number such las the position shown lby arrow 131 which is almost exactly over the decimal number 2. in this position it can bef.

-- seen that the sensing brush 37 makes electrical contact fastening'means 2,9, the gdiarneterlof aperture 531being'j y substantially equal to the diameter olf` fastening means 29. -i

so asy to establish good electrical'coi'itactl,therebetween.,Q60v Aperture lSti provided. in insulatingdisc .1.1 provides'for the insertion therethrough of fastening 'meansfif if t Discs -12r`through- 1.o `andbtheir associated lconductive I v,discs 2Q through'd areshown'intheir assernbledf'posi-` tions'in FIGURES s'throughl() respectively.v For" example, FIGURE 7 sets drththe insulating disc 13 wl1ichV has a plurality of raised portions 485,3 37, 83,' S9 which co` t operate with slots 3 2, 83, dfand S5 respectively :to form Y through. dforms ak coding pattern, thispattern being the l5 yis affplan'ar rde? Y the codedis'c for Zffbit position 'of thebinary code 5 l setforthvabove.` ltcan-be clearly seenf'tha-t" the lengthv and occurrence'of the `conductive portionsof the discsll K representation which 'set -withconductive segment 132701? tie ambiguity disc 24. Y

in this position the sensing brushes 35 and 31% may be misaligned so that theymake electrical contact'with segments 133 and 134 respectively, thereby producing a binaryA i forthr'i'n table 14d of FiGURE l5 onjthe line identifiedV by Varrow 136. Thus it can be seen `thatj due to va possible,v misalignment otA sensing brushes'd'and 3S with respect to, the code stack 25 of pears inthe binary representations shown'- in table" 1.35

f. `may therefore. appear atthe outputsfof `sensing"brushes 32 through 37... The lpossible combinations',thatmay'occur =under thesescircumstances are set forthin table' 140 of Y FiGURE liwherein vthe binary representations haveI been' writtenon lines which occupy positions midway between the vertical .decimal iiumberscolumii of vtable Milf-'Thus 'it can kbeseen that the possibil reconized-rather than avoided, as was yattemptedin the" velopmentoi the coded circular discsltfthrough Zdwherfeinthe darksegments re resent:the conductive,portions'of` prior artfl Thusiit can lbe seen upon consideringtable," v 'A leithat the .binary one in theambiguity position is.,`

A y i ityf'lorv ay niisalignnie'n't bejf tween-the code stack and the associated sensing brushes is present in every binary representation Whenever the sensing brushes occupy a position which is in the region of the transition between two decimal numbers of the dial face. Thus, since it is Ia practical impossibility to completely avoid erroneous readings, the ambiguity disc 24 recognizes the occurrence of this angular shaft position and transmits this reading accordingly. It can further be seenfrom the binary code set forth in table 140 that the binary representation for each position between two decimal numbers isunique and differs from the prior representation of any 'other such position.

Another coding arrangement which is set forth in FIG- URE 16 and which may be employed in encoder 25 shown in FIGURE 1 by substituting the disc arrangements of FIGURES 17 through 22 for the disc arrangements shown in FIGURES through l0, respectively, has a number of unique features which are not found in any other coding arrangement.

For purposes of illustrating the novelty of our code stack arrangement, consider the meter dials 39@ through 303 shown in FIGURE 23 wherein the dial 399 represents the least significant decimal digit and dial 393 represents the most signiticant decimal digit. Each dial has associated with it an indicating arm 3000i through 303:1, respectively, each arm being rotated by an associated shaft 30Gb through 303b, respectively, to which shaft the pointers 30th: through 303m are fixedly secured. Although meters of this general type may be arranged in any fashion, it will be assumed here that all indicating arms 30041 through 30361 rotate in the clockwise direction. It should further be understood that the meter dials are connected to one another by gear trains which have a 1 to l0 ratio between adjacent dials when considering the ratios in the direction from the least significant digit dial 309 to the most significant digit dial 303. The gear connections are represented schematically in FIGURE 23 by the dash lines 3M, 3dS and 396. Each shaft 309]? through 3ti3b has an encoder Sti-tic through 393e, respectively, cooperatively connected thereto which connections'are schematically represented by the dashed lines 36M through 3ti3d respectively. The encoders are ofthe same type as shown in FIGURE 2.

tually occupies a 36 .region between two such scale. markers. For example, the decimal number 1 occupies. .the angular region between scale markers 307 and 308 and the decimal number 2 occupies the angular region between scale markers 308 and 399. The transition from the decimal number 1 to the decimal number 2 takes place atthe instant that the indicating pointer -arm 30061 is in exact angular .alignment with scale marker 308. Since it is extremely ditlicult to tell whether the indicating arm is pointing to the decimal region between scale-markers 307 and 393 or the decimal 2 regionbetweenti and 309,

. the vregion which lies in close proximity tothe scale mark-v f ers, such as scale marker 308 for example, is known as 'an ambiguityor smear area.

The ambiguity area is. identitied by thefconductive portions ofthe ambiguity bit position conductive disc 24 l2; f tween two decimal numbers and 4.5 to the right of eac transition line. The ambiguity region is further identied as a smear between two decimal numbers as indicated by the presence of three binary ones out of the five binary bit positions which binary ones occur in the region from 9 to the left of a transition line, such as transition line 3M, up to the transition line, which three out of five code constitutes the logical sum of the binary Lone bits which are present in the two out of tive codes which represent the neighboring decimal numbers lying adjacent the transition line, as will be more fully described.

As can be seen, the indicator arm 309:1 through 303m represent the decimal number 3790. Indicator arm 391e apparently lies in the exact vertical angular alignment with angular scale marker 320. The code formed by the encoder for decimal 9 as can be Seen in FG. 16, lies at the transition line 32u and is a three out of rive binary code which also has a binary one in the ambiguity bit position. rThe presence of the binary one in the ambiguity bit-position identities the fact that a choice must be made as to whether the code generated by the encoder 301C which is associated with the dial face Still should represent decimal 8 or should represent decimal 9. The final determination is made however, by the condition of the code for least signicant decimal bit which is identified by dial 305i, which reads decimal 0. If, however, the least significant decimal bit was a 9, then it can clearly be seen that the choice to be made regarding the smear between decimal 8 and decimal 9 at dial 3M should be that ot the code representing the decimal 8.

As can clearly be seen, each 36 sweep of any one of the dials shown in FIGURE 23 is equivalent to a 360" sweep on the rdial immediately to its right, or, in other words, the dial of the next least signiiicant decimal digit. The novel data encoders, that is, the code stacks of our invention, when used in meters having dials of the nature of those shown in FIGURE 23, are extremely advantageous in that they serve to accurately identify which decimal representation is to be chosen when a smear condition is present. For example, in considering the dials 393 and 302, it lcan be seen since the next least significant bit to 3 is the decimal number 7, that the indicator armtia shouldv lie 25.2 below the scale marker 325 at the point' must represent a decimal 7 digit in order for the transmission to be correct. Although the circuitryv for performing this comparison operation isnot set forth in this applicatoin, such comparison circuitry may take many forms, one

typical form being set forth fully in copending U.S. application Serial Number 241,917, entitled Data Receiver,` filed December 3, 1962, by A. Brothman et al., and as-` signed tothe assignee of the instant invention.

(see FIG.' 16). l It can be seen from this figure that the leading edge,I such as for example, the leading edge 310 of f v.one conductive portion 315 lies 13.5 before'the line 311 which ,represents the transition romthedecimal 2` to the decimal 3, while the trailing-edge of conductive portion f'315'ofthe disc 24"k follows the line311by an angle of a be seen that veach conductive portion iden- Y '-ties'the ambiguity region which has been chosen as being v13.51to theleftotzeach line markingV the transition be- Thusour novel encoder providesa coding arrangement f which sets forth the following requirements whentransmitting ncodeddataffrom a meter having atleast twodecimal digit position encoders; i Y v (a) The-presenceof the code for`a decimalA 7,28, 9"' or O ina significant kdigit imposes the requirement.-` that l.

the code for the next most significant digit have -a binary fone state ambiguity bit,

(b) The-presence of the code for a decimal 'Sor 70 in a less:significant digit imposesthercquirement' that the code fornext most significant digit be in its 3-out-5 Inode.

(c) The presence of thecod'e for a 9 (clear or ami biguous) .demands that the lesser .of the two decimal nuinb'ers of the'next most significant! decimal digit s1near"` bejaecepted.

u (d) The presence of th-: codefori a decimal()-` (clear or i 'y ambiguous) demands that the greater of the two decimal numbers of the next mostk signiiicant digit smear be accepted. r y

This arrangement provides the highest degree of transmission reliability without resort to the technique kof double transmission which technique is too time consuming to be practicable. Y g

Referringspecically to FIGURE 16 table 130 sets forth the binary code arrangements for a iirst or nonambiguous code. The name non-ambiguous is ernployed since i-t refers to a code which represents 'a decimal digit which is in a position when being read that can clearly not be confused with any other decimal digit position. ASuch a position would be, for example, that shown by arrow 191 which lies clearly in the zone designatedvdecimal 5.

Each decimal digit from through 9 is represented in a Gray code which name is well known in the art as a name employed to distinguish the code from one in which each binary bit position has a weighted signicance such as, for example, a binary coded decimal representation. It should be noted that each binary representation diierrs from its neighboring binary representations by a shift of only one binary one For example the representation for decimal number has binary ones in the second and iifth positions (i.e., columns` 2 and 5 while the representations for decimal numbers 4 and 6 have binary ones in columns 3 and 5 and l and '2, respectively. Thus, only onebinary one position differs in adjacent representations .which acts to minimize er` roneous readings as will be more fully described. l

The second or ambiguous code shown'in table 131 y is a three out of five code in that each binary representation contains a binary ones in three out of the iive columns l through 5. It should be noted that `each binary representation differs from every other binary representation. In addition, .it should be noted that ambiguity code containsa binary one in each column that the neighboringV binary representations of the iirst code ofv table 180 contain lbinary onef For example,

.193 from the l'eltV (i.e.,column 2 as shown in Vtable'ltitb).`

the binary? representation inthe first code' is 00101 for decimal 4 andV 01001for decimal 5- (see numerals v19t) and 191); ,'"The binary/representation in the second code for the transitionftrom decimal 4 to'decimal 5 is 01101 (see numeral 192). Thus, in moving from an unambiguousdecimal 4 reading to the ,crossover or transition region between 4 and 5 anV ambiguity region produces'the code'01101 which ditfersifrom decimal 'y y2 out of Scode and the ambiguous 3 out of 5 code. This` 4 bythe presence of a binary on'e'i n the second position In moving from 1Vthe ambiguous yreading 01101 to the decimal 5 representation, 01001 the decimal 5; representationuditersfromthe ambiguous reading by the; labsence by numeral 1941).m Y Y v Thus it should be noted that in moving from first kcode representations to' second representations andfthenbacirk to first code representations, the electricaly connectimor only onesensing-brushl iseeither completed br severed Yattion ftflo.,241,917,1 entitled KfData Receiver.

-'Ilfhe binary representations'.in` columns 6 vottablesy 180 nd '181 serve to identify the code, being sensed at th'eiin-` of a binaryfone 1in thethird 'position fromthe'lefttiie.

column ,Zas shown .in table 1580' andgthe rowzdesignated' one time.- Therefore,-although`.theremay ,be vsome uncertainty in the digit representation withregard to .which ofthe two adjacent sections isbeing sensed, the possibility of obtaining `an'erroneous,indication ofsome/remote l SectionV is avoided. However, this Vuncertainty caneasilyj- 4 be resolvedand the decisiiin as to which decimal is correct l' can be madepwitha high-degree of naccuracy at`the rel yceiving end byV logicalafdecision 'making circuitry similarl to that disclosedV in aforementionedVV UQS. patent applicaf discs may be the 3 out of 5.(ambiguous) code. Ir" the readout is 010101 this denotes either the decimal 7 or an erroneous reading and the decision as to which is true must be made at the receiving end based upon the state ofthe next least sig'- niicant digit as explained in patent application Data Receiver, US. application No. 241,917, mentioned previously. If the readout is 010111 a decision must be made as to whether -it is a 7 or S at the receiving end logic since a binary one in the Vright-hand most position should be accompanied with binary ones in three of the tive left-hand most digit positions (Le. columns l-5 of tables and 185).

It can be seen in FIGURE 16 that the ambiguity dise 24 is conductive (i.e., makes Contact with its associated sensing brush) 131/2o to the left and i1/2 to the right ofl the transition hairline between adjacent digits. This enables the misalignment ofl sensing brushes to he as great as that shown by centerlines and 196. l

The conducting and insulating discs employed in the modied code arrangement of FIGURE 16 are shown in FIGURES 17 through 22 wherein A the only distinction- A binary one in column six of table 18% serves asl the` means for identifying the approach of ari ambiguous 3 out of 5 code, i.e., the transition between the unambiguous unique arrangement of the conductive segments insures a make Contact before break Contact action of the-brushes. It should be noted that each disc 19 through 2.3i (see FIGURES 17-21) contains two notches and that the notches are identicalin arcuate length. The only distinction between thediscs Aof FIGURES l7through 21 is that they are angularly displaced with respect to one another (as shown in FIGURE 16) so that angular relations between the notches and the apertures such las apertures S32-d0 and the notches`S1-52f is `diierent in each' disc-19 through 2e so thatfall insulating and conducting p made l*from one die While the apertures may be made a'fterfeachdisc is formed. A

Y It-should be Ifain-ther noted thatgthe. unique code ar# rangement btp-,FIGURE 16 may be vutilised so that the vref ionsot each discoftthefcode stack which are identiiie'd'Vv byy binaryfO ambiguity bitposition may bey changed-` to the binary lcondition while thegrgions identitied by binaryV onew'inthe ambiguity bit positionmay bechanged to the -L binary O condition.l "Thus thef out. of 5 arrangeme'ity 5 may be :employedto` reprersentthe'noneambiguous lareas.-

whlythe 2 out of Sfcodemay be employed torepresent 'the ambiguous areas yot'jthe `decimal numbers'on Vthe dial faces 390-303 shown inllIGURE 23.,V The only? change stan't' position readout is givenf 4Column' lof table1ii i contains a biha'ry zero foreachandevery decimalliiP- resentatiqniin the first jcode :thereby identifying fthe 'pres-fl i which need be made is-thfatof retaining the ambiguity disc .7; conductivepontions in their original positions'.` Thus it ZOy as an alternative to the vmake before break code arrange-v is possible tofform ay break beforeV maire` code arrangement ment oit-FIGURE .16Q t lThe break before make-code varrangement is setkfo'rth FIGURE 24 while the tables rangements respectively the disc determine the coding and'liilshow the 3 outof 5 and 24outgoff5fcodear-A vvhei'ein'it-should berief dhatx:

the code arrangements of Figure 24 is the inverse of the code arrangements of FIGURE 16..

` FIGURE 12 shows one sensing brush such as sensing brush 31 inserted through insulating post 38. The end 31a of sensing brush 31 bears upon the inner perimeter of disc 18 and is biased in such a manner as to impose a force upon disc 18, in the direction shown by arrow 147, that being radially inward with respect to rotatable shaft 26. It can be seen that since there are seven sensing brushes 31 through 37, the individual forces exerted yield a total force exerted upon rotatable shaft 26 is seven times as great as the force exerted upon rotatable shaft 26 by individual sensing brush 31. The brush is positioned in such a way as to oppose the separating force associated with spur gear set in order to diminish the drag effect that the encoder assembly will of necessity apply to the gear train. The purpose of this radial force is for the following reason:

FIGURE 1l shows a pair of cooperating gears 153 and 159 whereby gear 15S is driven into counter-clockwise rotation as shown lby arrow 153- under the inuence of gear 159. Gear 158 may, for example, be connected or mounted upon rotatable shaft 126. The force resulting upon gear 153 by 159 is shown by force Vector 151). The reason that vector 150 assumes the direction it does is that in order to experience a rolling action (rather than a sliding action) with tooth 155 causes the force 150 to act at an angle 6 to a line joining .fthe centers of the two gears. This angle is 'usually either 75 .5 of 70 depending upon whether high speed or low speed application, respectively, is desired. The force imparted by gear 159 acts normal to the edge of tooth resulting in force vector 150.

This vector resolves itself into radial (separation) and tangential (driving) component vectors 151 and 152, respectively. Tangential (driving) vector 152 acts to drive gear 158 into rotation in the` direction shown by arrow 153 whereas radially directed vector 151 acts to urge gear' 15S to separate from 159. Force 157 shows in FIGURE 11 which is the resultant force of the forces without coderstaeks atlixedthefeoshown). T hel electrical connection between' the conduca 147 of each sensing brush such as brush 31 is directed so that it is equal and opposite to force Vector 151 thereby acting as an auxialiary bearing which acts in such a way as to add no drag to the meterdue to the mounting of the code stack upon the meter movement.

Thus it can be seen that the addition of my novel :code

` FIGURE 13 shows a schematic diagram for connecting ductor.. This arrangement greatly A'reduces the number of leads needed Vbetween the sensing brushes over prior arty E@ 167 through connection 160, resistor 172 Ito the rst track wire 175. Also, from zero track wire 175, a conductive path exists through resistor 173, closed connection 162 and resistor 168 to ground potential 176 (no positive voltage is impressed at point 169). A palth parallel to this path consists of resistor 174 connected to the rst track line 175 through closed connection 164, resistor 170 to ground potential 176 (no positive voltage is impressed at point 171). This portionof the circuit is set forth in FIGURE 14.

1t should be noted that normally a conductive path does not exist at points 162 and 164 but this example is offered here to set forth the worst possible condition in order to point out the effect upon the encoded readout of the arrangement of FIGURE 13. Resistors 172, 173 and 174` are each 20- kilohms, for example,- while resistances 168 and 171B are one kilohm each. Thus it can be seen that in this condition, the voltage divider which consists of resistor 172, the parallel resistances 173-168 and 1711-174, divide the 48 volt input impressed at common point 167 so the 1/as of the 48 volt input appears at the zerof track conductor 175. This naturally assumes that all three contact sets of the first track are closed at the same instant. It canbe seen that if only one of the two Contact sets 162. and 164 are closed at the time that contact connection 16) is closed, then one-half of the 48 volt input will appear at the first track conductor 175, while if connections 162 and 164 are both open at the time con- .nection is closed and being read then the entire `48 volt input will appear at the `first track conductor 175;

Thus, upon, the appearance of less than 1/3' of the input voltage at the first track conductor 175, this indicates a binary zero condition whereas any value equal to or greater than 1/3 of the input voltage (i.e., equal to or greater than 16 volts) appearing at the tir-st track line conductor 175-indicates a binary one condition at the conductive disc 19 which represents the decimal' zero bit position of the Zout of 5 code. Every other track,

such as the tracks l, 2, 3, 6 and Ambiguity (Amb),-is connected in the same exact manner as the iirst track conarrangements. For example, without the arrangement shown in FIGURE 14, six-leads `are needed for the sixV binary. positions and one lead is needed forvthe common lead. Thus 7 leadsare needed for each Vcodestack, and

Y in the example of FTGURE 14 since there are three code a plurality of code stacks suchv as the code stackassembly n 25 ofFIGURE 1 to an output' untilization devicen (not tive disc` 19 and its associated sensingbrush32 rwhich represents the 50? track is represented by the `symbol -160- whereas no electricalconnection is representedfby the symbol'f161 shown between Vconductive segment and sensing brush 33 'shown inFGURE 13. The manner of operation isv as follows:

#Only one code stack assemblage, such as code stack rassemblage 16a of the three vcode stackassemblages 11m I through 10e, is read at a time'. `This'serial 'selective readout is performed by impressing a positive DC. voltage `atl points (167,' 169 and 171 in serial fashion in'any well V knownfmanner such as, for example, by stepping switch 250.' At theV instant that code stack assemblage 10a is being sensed, a positive voltage is impressed at common point 16'7 .whereas no voltage is impressed at common points; 16StandV 171 by any well known means. Alt' this instant, assuming contact is made between lsensing brush 32, and y'conductive disc 19 as shown by symbol 160,-thel conductive pathis as follows:

i From apositivevoltage, 4for exariiple, `48 volts at 'point rangement `of `FlGURE 14v only .6 wires ,for the binary l representations,` and three wiresforfthe commons are needed, giving'a total of 9vwires needed between the code; Y stacks,Y 10av through .10c and the youtputwutilizvation device.

This resultsvin a saving over half the wiresneeded in the g prior art arrangement.` Although FIGURElS showsan arrangement wherein onlythree encoders 10m/10b and 10care wiredtothe logical OR readout arrangement ,it

should be understood that any number of ,encoders may [beV wired, in this `fashion wherein therworstfcondition for a v binary one voltagefis and for a binary yzero voltage 1s aswas previouslyldescribed. 1

The insertion ofthe resistahces A be performed as shown in FiGURE 12fwherein the sens- 17 of a utilization device. Thus a resistor 31!) serves as both the needed resistance value as required in the schematic of FIGURE 14 and as the sensing brush 31 which cooperates with the conductive disc 18.

The resistance needed may also be added by forming -the conductive discs 19 through 24 (or 19' through 24') of a material having resistivity of the order of the resistances employed in FIGURE 13 or by applying a resistive coating upon the conductive edges of the discs 19 through 24 which come into engagement with their associated sensing members 31 through 37 respectively (see FIGURE l).

It can therefore be seen that we have provided a novel code stack which is designed so that it can be manufactured at low cost and which has a novel coding arrangement for the recognition of ambiguous readings. The code stack is mounted with respect to the normal utility meter gearing systems in such a manner as to introduce no appreciable drag and thereby does not change the sensitivity in such meters. Employment of a plurality of code stacks for meters having a plurality of dial faces such as Water, gas and electric meters presently in use permits the connection between the plurality of code stacks and the utilization connected thereto to be performed in a relatively simple manner since less than half the number of conductors are required as opposed to the number needed in prior art devices.

In the foregoing, We have described our invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of our invention Within the scope of the description herein are obvious. Accordingly, We prefer to be bound not by the specific disclosure herein but only by the appending claims.

We claim:

1. A shaft angle encoder comprising first rotatable means capable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of said signal groups repre senting one discrete angular portion of a complete circle of revolution, second means for recognizing Vshaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, said second means including third means for generating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first rotatable means comprising a plurality of conductive discs, a plurality of insulating discs, said conductive and insulating discs being stacked in alternating fashion for insulating the faces of said conductive discs each from the other, said arrangement being adapted for mounting to a rotatable shaft, each of said insulating discs having at least one projection on Y a face thereof, the projections of each of said insulating discs having a first side concentric with the arcuate periphery of its associated conductive disc, the first arcuate sides of each of said projections on each insulating disc differing in length from the first arcuate sides of the remaining projections.

2. A shaft angle encoder comprising first rotatable means capable of assuming a plurality of discrete angular positions for generating a first pluralityA ofkbinary coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, said second means including third means for generating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first rotatable means comprising a plurality of conductive discs, a plurality of insulating discs, said conductive and insulating discs beingstacked in alternating fashion for insulating said conductive discs each from the other, said arrangement being adapted for mounting to a rotatable shaft, each of said insulating discs having at least one projection, the projections of each of said insulating discs having a rst side concentric with the arcuate periphery of its associated conductive disc, the first arcuate sides of each of said projections differing in length from the first arcuate sides of the remaining projections, each of said conductive discs having at least one notch along its periphery, the notch of each conductive disc having a configuration which is adapted to receive the arcuate projection of its associated insulating disc.

3. A shaft angle encoder comprising first rotatable means adapted for mounting to a shaft capable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, said second means including third means for generating a second binary coded signal groups Which are adapted to be easily distinguishable from said first binary coded signal groups, said first rotatable means comprising a plurality of conductive discs, a plurality of insulating discs, said conductive and insulating discs being stacked in alternating fashion for insulating said conductive discs each from the other, said arrangement being adapted for mounting to a rotatable shaft, each of said insulating discs having at least one projection, the projections of each of said insulating discs having a first side concentric with the .arcuate periphery of its associated conductive disc, the first arcuate sides of each of said projections differing in length from the first arcuate sides of the remaining projections, said conductive and said insulating discs having first and second centrally located apentures respectively, said first apertures having a diameter greater than the diameter of said shaft to be electrically insulated therefrom, said second apertures having a diameter substantially equal to the diameter of said shaft to cause the rotation of said shaft to be imparted to said insulating discs, said projections and said slots cooperating to impart rotation of said insulating discs to said conductive discs.

4. A shaft angle encoder comprising first rotatable means capable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, said second means including third means for generating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first rotatable means comprising a plurality of conductive discs, a plurality of insulating discs, said conductive and insulating discs being stacked in alternating fashion for insulating said conductive discs each from the other, said arrangement being adapted for mounting to a rotatable shaft, each of said insulating discs having at least one projection, the projections of each of said insulating discs having a first side concentric with the arcuate periphery of its associatedconductive disc, the first arcuate sides of each of said projections differing in length from the first arcuate sides of the remaining projections, said conductive and said insulating discs having first and second apertures positioned a predetermined distance aWay from the axes of said discs, a cylindrical conductive means inserted through said apertures for establishing a conductive path between each of said conductive discs, said cylindrical means including fastening means for securing said discs to form a unitary assembly.

5. A shaft angle encoder comprising first rotatable means capable of assuming a plurality of discrete angular positions for generating a first plurality of binary 19 coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions whichv lie in the `immediate region surrounding the adjacent ends of neighboring angular portions, said second means including third means for generating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first means including means for generating said first binary coded signal groups in a twoout-of-five binary code arrangement wherein all of said code groups differ from each other, said third means including means for generating said second binary coded signal groups in a three-out-of-five binary code arrangement wherein each of said code groups differ from each other. Y

6. A shaft angle encoder comprising first rotatable means capable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions which lie in the immediate region surrounding the adjecent ends of neighboring angular portions, said second means including third means for gener-ating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, fourth means for sensing the binary coded signal groups, said yfourth means being adapted to sense the binary coded signal group which correctly represents the angular position of said first and second means regardless of the position of said first and second means, said fourth means including means to generate a binary bit wherein one state of said bit identifies said first code group and the opposite state identifies said second codel group.y

7. A shaft angle encoder comprising rst rotatable means capable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of'said signal group-s representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, said second means including third means for generating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first means including means for generating said first binary coded signal groups in a two-out-of-five binary code arrangement wherein all of said code groups differ from each other, said third means including means for generating said second binary coded signal groups in a three-out-offive binary code arrangement wherein each of said code groups differ from each other, and wherein each of said second code groups differs from the adjacent second code groups in only one bit position.

8. A shaft angle encoder comprising first rotatable means capable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions in the immediate region surrounding the adjacent ends of neighboring angular positions, said second` means including third means for generating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first means including means for generating said first binary coded signal groups in a two-out-of-five binary code arrangement wherein all of said code groups differ from each other, said third means including. means for generating said second binary coded signal groups in a three-out-of-ve binary code arrangement wherein cach of said code groups differ from each other and wherein each of said second code groups differs from the adjacent second code groups in only one bit position, each of said second code groups vbeing the composite of the adjacent first code groups.

said sec-ond means including third means for gen-A erating a second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, said first rotatable means comprising a plurality of conductive discs, a plurality of insulating discs, said conductive and insulating discs being stackedy in alternating fashion for insulating said conductive discs each from the other, said arrangement being adapted for mounting to a rotatable shaft, the outer diameter of said insulating discs being greater than the outer diameter of said conductive discs forming a plurality of substantially U-shaped grooves, a plurality of sensing members each being positioned to bear upon an associated conductive disc, said substantially U-shaped grooves being adapted to guide the ,associated sensing member in said groove, impedance means each having a first terminal connected to an associated sensing member, the opposite end of impedance means connected to like sensing members of each of said encoders being connected in common, means for selectively connecting a positive voltage to only one of said encoders at any given instant, the outputs of the said energized encoders appearing at said common points in parallel fashion.

10. A shaft angle encoder comprising first rotatable meanscapable of assuming a plurality of discrete angular positions for generating a first plurality of binary coded signal groups, each of said signal groups representing one discrete angular portion of a complete circle of revolution, second means for recognizing shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, ysaid second means includ-` ing third means for generating second binary coded signal groups which are adapted to be easily distinguishable from said first binary coded signal groups, fourth means for sensing the binary coded signal groups, said fourth means being adapted to sense the binary coded signal group which correctly represents the :angular position of said first and second means regardless of the position of said first and second means, said fourth means including means to generate a binary bit wherein one state of said bit identifies said first code group and the opposite state identifies said second code group, the reading portion of the said one state of said bit being further a-dapted to identify the immediate approach of said second code group.

11. A meter for encoding a kdecimal reading of a quantity being measured wherein said decimal reading is at least two decimal digits in length; first and second means each mounted on rotatable shafts for digitizing the angular positions of the meter utilized to identify by a decimal number the quantity being measured; gear means for imparting rotation in a 1:10 ratio to one of said shafts in responseto rotation of the other of said shafts; said first and second means each being comprised'of a rotatable drum capable of assuming any angular position in a complete circle of rotation; said circle being divided into a plurality of discrete angular portions; rst conductive means on the surface of said drum for generating a first v plural-ity of binary coded signal groups wherein each one of said signal groups represents one of said discrete angular portions around said circle; second conductive means on said drum for identifying shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions; said second conductive means cooperating with said first conductive means to generate a second plurality of binary coded signal groups 21 l to identify an angular shaft position in the immediate region of two adjacent angular portions; stationary sensing means making wiping contact with the surface of said drum for reading out said binary coded signal groups; said second code group being adapted to identify a iirst range in which the least significant decimal digit will lie when one of said second binary coded groups is read out by said sensing means; said rst code being a two-out-of-ive binary code; said second code being a three-out-o-f-iive code.

12. A meter for encoding a decimal reading of a quantity being measured wherein said decimal reading is at least two decimal digits in length; first and second means each mounted on rotatable shafts for digitizing the angular positions of the meter utilized'to identify by a decimal number the quantity being measured; gear means for imparting rotation in a 1:10 natio to one of said shafts in response to rotation of the other of said shafts; said first and second means each being comprised of a rotatable drum capable of assuming any angular position in a complete circle of rotation; said circle being divided into a plurality of discrete angular portions; rst conductive means on the surface of said drum for generating a rst plurality of binary coded signal groups wherein each one of said signal groups represents one of said discrete angular portions around said circle; second conductive means on said drum for identifying shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angularv portions; said second conductive means cooperating with said first conductive means to generate a second plurality of binary coded signal groups to identify an angular shaft position lin the immediate region of two adjacent Iangular portions; stationary sensing means making a wiping contact with the surface of said drum for reading out said binary coded signal groups; said second code group being adapted to identify a rst range in which the least significant decimal digit will lie when one of said second binary coded groups is read out by said sensing means; said iirst code being a tWo-out-of-iive binary code; said second code being a three-out-of-ve code, third conductive means on said drum surface for generating a plunality of third binary coded signal groups to identify a second range in which the least signiiicant decimal digit will lie when one of said second binary coded groups is read out by said sensing means, said second range being smaller than said irst range; said third code beinga four-out-of-six code.

13. A shaft :angle encoder comprising first rotatable means capable of assuming any angular position in a complete circle of revolution, said circle being divided into a plurality of discrete angular portions; said first rotatable means comprising second means for generating a first plurality of binary coded signal groups, each of said signal groups representing one of said discrete angular positions making up said circle; third means on said first rotatable means for identifying shaft angle positions which lie in the immediate region surrounding the adjacent ends of neighboring angular portions, third means including fourth means for generating second binary coded signal groups which are adapted to be easily distinguishable from said iirst binary coded signal groups to identify an angular position in the immediate region of two adjacent angular portions; said second means and said third means comprising a plurality of substantially circular conductive means for generating said binary coded signal groups; means for electrically insulating said conductive means from one another.

References Cited in the le of this patent UNITED STATES PATENTS 2,764,344 Wescott Sept. 25, 1956 2,972,740 Lahti Feb. 21, 1961 3,022,500 Stupar Feb. 20, 1962 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,165,733 January 12, 1965 Abraham Brothman et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 4, lines 10 and 11, for "Serial Number 71,093, now Patent No. 3,096,932, entitled "Automated Meter Reading System," by" read Seria1 No. 91,043, now Patent No.

3,142,726 entitled "Automated Sequential Interrogation Meter Reading System Over Telephone Lines," by

Signed and sealed this 10th day of August 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Atesting Officer g Commissioner of Patents 

12. A METER FOR ENCODING A DECIMAL READING OF A QUANTITY BEING MEASURED WHEREIN SAID DECIMAL READING IS AT LEAST TWO DECIMAL DIGITS IN LENGTH; FIRST AND SECOND MEANS EACH MOUNTED ON ROTATABLE SHAFTS FOR DIGITIZING THE ANGULAR POSITIONS OF THE METER UTILIZED TO IDENTIFY BY A DECIMAL NUMBER THE QUANTITY BEING MEASURED; GEAR MEANS FOR IMPARTING ROTATION IN A 1:10 RATIO TO ONE OF SAID SHAFTS IN RESPONSVE TO ROTATION OF THE OTHER OF SAID SHAFTS; SAID FIRST AND SECOND MEANS EACH BEING COMPRISED OF A ROTATABLE DRUM CAPABLE OF ASSUMING ANGULAR POSITION IN A COMPLETE CIRCLE OF ROTATION; SAID CIRCLE BEING DIVIDED INTO A PLURALITY OD DISCRETE ANGULAR PORTIONS; FIRST CONDUCTIVE MEANS ON THE SURFACE OF SAID DRUM FOR GENERATING A FIRST PLURALITY OF BINARY CODED SIGNAL GROUPS WHEREIN EACH ONE OF SAID SIGNAL GROUPS REPRESENTS ONE OF SAID DISCRETE ANGULAR PORTIONS AROUND SAID CIRCLE; SECOND CONDUCTIVE MEANS ON SAID DRUM FOR IDENTIFYING SHAFT ANGLE POSITIONS WHICH LIE IN THE IMMEDIATE REGION SURROUNDING THE ADJACENT ENDS OF NEIGHBORING ANGULAR PORTIONS; SAID SECOND CONDUCTIVE MEANS COOPERATING WITH SAID FIRST CONDUCTIVE MEANS TO GENERATE A SECOND PLURALITY OF BINARY CODED SIGNAL GROUPS TO IDENTIFY AN ANGULAR SHAFT POSITION IN THE IMMEDIATE REGION OF TWO ADJACENT ANGULAR PORTIONS; STATIONARY SENSING MEANS MARKING A WIPING CONTACT WITH SURFACE OF SAID DRUM FOR READING OUT SAID BINARY CODED SIGNAL GROUPS; SAID SECOND CODE GROUP BEING ADAPTED TO IDENTIFY A FIRST RANGE IN WHICH THE LEAST SIGNIFICANT DECIMAL DIGIT WILL LIE WHEN ONE OF SAID SECOND BINARY CODED GROUPS IS READ OUT BY SAID SENSING MEANS; SAID FIRST CODE BEING A TWO-OUT-OF-FIVE BINAR CODE; SAID SECOND CODE BEING A THREE-OUT-OF-FIVE CODE, THIRD CONDUCTIVE MEANS ON SAID DRUM SURFACE FOR GENERATING A PLURALITY OF THIRD BINARY CODED SIGNAL GROUPS TO IDENTIFY A SECOND RANGE IN WHICH THE LEAST SIGNIFICANT DECIMAL DIGIT WILL LIE WHEN ONE OF SAID SECOND BINARY CODED GOUPS IS READ OUT BY SAID SENSING MEANS, SAID SECOND RANGE BEING SMALLER THAN SAID FIRST RANGE; SAID THIRD CODE BEING A FOUR-OUT-OF-SIX CODE. 